The proposed study will explore the hypothesis that ~voices~ or speech hallucinations (SHs) arise from alterations of the working memory component of speech perception networks. This hypothesis derives from a preliminary study comparing performance of simulated speech perception neural networks and human speech tracking. The pattern of speech perception Impairments demonstrated by schizophrenic patients with SHs was simulated by reducing connectivity of working memory networks and enhancing neuronal excitability. Funding is sought to replicate and expand this research initiative. A more complex version of the earlier simulation of the speech perception will be used to model hallucinations that express whole phrases or sentences. These simulations will then be used to predict speech shadowing performance of patients reporting SHs. Comparative empirical data will be provided by 25 schizophrenic patients with SHs, 25 schizophrenic patients without this symptom, and 25 normal controls. Subjects will be administered the babble-masked speech shadowing task and an auditory version of the continuous performance task (CPT). The following is predicted: (I) speech shadowing performance of patients with SHs will be most closely simulated by neural networks reflecting reduced working memory connectivity and increased neuronal excitability; (ii) speech perception impairments will not significantly covary with other positive symptoms, negative symptoms, or CPT performance; (iii) patients with SHs will tend to demonstrate semantically linked word illusions when listening to phonetic noise whereas illusions elicited in normals and nonhallucinators will reflect a random selection of words and phrases; (iv) hallucinators will demonstrate especially pronounced verbal working memory deficits. Confirmation of these predictions would provide testable models linking neuroanatomic and neuromodulatory alterations of verbal working memory, hallucinated "voices," and speech perception impairments.